A new way to measure the turbulence of large planets and exoplanets

Two gas giants Jupiter and Saturn are harsh and turbulent places. Their turbulence produces cascades of energy, a non-linear energy transfer between different scales of motion.

These are as crucial to understanding planetary dynamics as the cardiovascular system is to understanding the human body.

But there is no reliable way to quantify planetary turbulence, until now.

Now, scientists from the University of Rome have shown that the energy transfer rate of turbulence can be calculated relatively quickly from a variable related to planetary rotation and known as potential vorticity (PV).

The method was first developed by Galperin and his graduate student, Jesse Hoemann, and tested in experiments conducted at the University of Rome during Jesse’s visit. The method was confirmed using actual velocity data extracted from Jupiter cloud motion images captured by the 20-year-old Cassini mission, further laboratory results performed in a rotating tank at the University of Rome in Italy, and computer simulations for Saturn.

Based on the PV calculations, the team showed for the first time that the rate of energy transfer in Jupiter’s atmosphere is four times faster than that of Saturn.

Like basic physical laws, the laws of turbulence are universal; hence the method can now be applied to other natural environments such as the ocean.

Galperin said, “Eddies in the Earth’s ocean that resemble eddies on Jupiter, for example, have varying strengths, sizes, and durations and are critical to understanding Earth’s balances of energy, heat, salt, carbon dioxide and more.”

Lead author Simon Cabanes, Ph.D., postdoc at the Department of Civil and Environmental Engineering (DICEA) of the University of Rome La Sapienza said: “This is the first estimate of Saturn’s turbulent power from observations, and this study opens the way for future analysis of data in other planetary atmospheres.”

Journal reference:

1. Simon Cabanes et al. Revealing the intensity of turbulent energy transfer in planetary atmospheres, Geophysical Research Letters (2020). DOI: 10.1029 / 2020GL088685